1. Field of the Invention
The present invention relates to a media contents distribution system, and more particularly to a system for distributing a multimedia content containing video data and/or audio data to users, while preventing unauthorized use thereof.
2. Description of the Background Art
In recent years, network systems have been developed as part of the social infrastructure, and consequently, multimedia contents containing digital data such as images, moving pictures, and audio are widely spread via such networks. Moreover, large-capacity recording media have been developed, making it possible to distribute multimedia contents via such recording media. Digital data is easy to preserve and duplicate, and does not deteriorate in quality through preservation or duplication. As a result, if unauthorized preservation or duplication of media contents containing digital data is committed by a recipient, the rights of the author of such media contents are infringed, thus detracting from the profit of the provider of the media contents. In order to prevent this situation, when distributing any media content containing digital data, it is necessary to impose certain limitations on the use of the media content by users.
Conventionally, the limitation on the use of media contents has been realized by, for example, encrypting digital data. Another alternative has been to ensure that a user makes an agreement concerning the use of a media content at the time of purchasing the media content, after which the limitation on the use of the media content is left up to the conscience of the user.
However, even if digital data is encrypted, a decryption key for decrypting the encrypted digital data may be stolen, so that it is still impossible to completely prevent unauthorized preservation or duplication of media contents by the recipients. Any agreement directed to the limitation of the use of a media content cannot guarantee that the agreement will be abided by.
A multimedia content is characterized in that, once purchased, it can be played back or viewed an unlimited number of times, substantially perpetually. On the other hand, from the perspective of the user, some media contents are only needed for a certain period of time and never again thereafter. In particular, as the amount of a single media content increases, which is currently the case, the data which is really needed by a user may often be only a part of the purchased media content. Even in such cases, however, the user is still paying a fee which often far exceeds what should be the real price in view of the extent to which the user has actually used the media content.
Therefore, from the perspective of the provider of a media content, a system is desired which can effectively limit the use of a media content by a user; and from the perspective of the user, a system is desired which only requires the user to pay a price according to the extent to which the user has actually used the media content, in exchange for somewhat limited usage. There have not been known any such systems to date.